This proposal requests support for a Nutrition and Physical Activity Assessment Study within the Observational Study (OS) component of the Women's Health Initiative (WHI). The OS cohort is comprised of 93,676 postmenopausal women in the age range 50-79 when enrolled at the 40 WHI Clinical Centers in the U.S. between 1994 -1998. The study will be conducted among 450 postmenopausal weight-stable women with oversampling of racial/ethnic minority women and of women in the extremes of body mass index. Participating women will complete the same food frequency questionnaire (FFQ) and physical activity questionnaire used at screening for WHI enrollment, a four-day food record (4DFR) as was used at baseline in the WHI Dietary Modification Trial (48,835 women), and other selected dietary and physical activity assessments (three 24-hour dietary recalls, a physical activity frequency questionnaire, social desirability measures, and a 7-day physical activity recall). Participating women will follow a doubly-labeled water protocol to objectively assess total energy expenditure and an indirect calorimetry protocol to assess resting energy expenditure, thereby also yielding an objective assessment of activity-related energy expenditure. The expenditure of protein, sodium, and potassium will also be assessed from urine specimens, and the concentrations of selected nutrients will be measured in blood specimens. These data will be used to evaluate and contrast measurement properties of the dietary and physical activity assessment tools and their combination, with an emphasis on: systematic bias as a function of body mass, ethnicity, age, and other individual characteristics; the magnitude of person- specific and random measurement error variances; and the correlation patterns among errors from differing assessment procedures. Additionally, the data will be used to calibrate the FFQ, 4DFR, and physical activity questionnaire data collected at baseline, and subsequently, in the WHI, for use in a range of analyses to associate dietary and physical activity patterns with weight change and disease risk over an average 10-year follow-up period among 161,808 women in the WHI Clinical Trial and Observational Study. The study will provide much needed data regarding dietary and physical activity assessment in an understudied segment of the U.S. population, and will provide crucial information for interpreting existing studies and for future study planning. [unreadable] [unreadable] [unreadable]